The role of the pineal complex in reproduction, thermoregulation, rhythmicity and behavior will be studied in appropriate species, including fish, reptiles, and mammals. Goals for the coming year are: (1) Continue investigations of the role of pineal bodies in regulation of body temperature and metabolism, using ectotherms (lizards, alligators, snakes) and endotherms (squirrels, armadillos, opossums). (2) Investigate the potential role of the pineal complex, particularly the parietal eye of lizards, in aggressive behavior. (3) Determine if there are differences in behavior and metabolic physiology among animals with pineal organs (the very great majority) and some few that lack them (e.g. alligators and armadillos). (4) Continue to be interested in extra-pineal sources of melatonin (the pineal-characteristic hormone) including retinae, and to search for melatonin receptors in these sites. (5) Further study of the role of pineal organs in rhythmic behavior in fishes, reptiles, and mammals.